
  
  <template>
    <div style="display: flex;position: relative">
        <div class="box" :style="minImgBoxStyle" @mouseleave="mouseLeave" @mouseenter="mouseEnter"
            @mousemove="mousemove($event)">
            <!--原始照片-小照片-->
            <img :style="minImgStyle" fit="contain" ref="minImg" :src="finalMinIMGsrc" />
            <!--探测块-->
            <div v-show="show" class="areaMark" :style="areaMarkStyle"></div>
        </div>
        <div class="box maxImgBox" :style="maxImgBoxStyle" v-show="show">
            <!--放大后的照片-->
            <img :style="maxImgStyle" fit="contain" :src="finalMaxIMGsrc" />
        </div>
    </div>
</template>
<script>
export default {
    props: {
        minIMGsrc: String,
        maxIMGsrc: String,
        scale: {
            type: Number,
            default: 2
        },
        width: {
            type: Number,
            default: 420
        },
        height: {
            type: Number,
            default: 420
        },
    },
    data() {
        return {
            show: false,
            finalMinIMGsrc: '',
            finalMaxIMGsrc: '',
            imgBoxWidth: 420,
            imgBoxHeight: 420,
            areaWidth: 210,
            areaHeight: 210,
            areaMarkStyle: {},
            minImgBoxStyle: {
                cursor: 'move'
            },
            minImgStyle: {},
            maxImgBoxStyle: {


            },
            maxImgStyle: {
                position: 'absolute',
            },
        }
    },
    watch: {
        'minIMGsrc'() {
            this.init()
        },
        'maxIMGsrc'() {
            this.init()
        },
    },
    mounted() {
        this.init()
    },
    methods: {
        init() {
            this.imgBoxWidth = this.width
            this.imgBoxHeight = this.height
            this.$set(this.minImgStyle, 'width', this.imgBoxWidth + 'px')
            this.$set(this.minImgStyle, 'height', this.imgBoxHeight + 'px')
            this.$set(this.maxImgStyle, 'width', this.imgBoxWidth + 'px')
            this.$set(this.maxImgStyle, 'height', this.imgBoxHeight + 'px')
            this.$set(this.minImgBoxStyle, 'width', this.imgBoxWidth + 'px')
            this.$set(this.minImgBoxStyle, 'height', this.imgBoxHeight + 'px')
            this.$set(this.maxImgBoxStyle, 'width', this.imgBoxWidth + 'px')
            this.$set(this.maxImgBoxStyle, 'height', this.imgBoxHeight + 'px')
            this.$set(this.maxImgBoxStyle, 'left', this.imgBoxWidth + 'px')
            this.areaWidth = this.imgBoxWidth / this.scale
            this.areaHeight = this.imgBoxHeight / this.scale
            this.finalMinIMGsrc = this.minIMGsrc
            if (!this.maxIMGsrc) {
                this.finalMaxIMGsrc = this.minIMGsrc
            }
            this.$set(this.areaMarkStyle, 'width', this.areaWidth + 'px')
            this.$set(this.areaMarkStyle, 'height', this.areaHeight + 'px')
            this.$set(this.maxImgStyle, 'transform', 'scale(' + this.scale + ')')
        },
        mouseEnter() {
            this.show = true
        },
        mouseLeave() {
            this.show = false
        },
        mousemove(e) {
            // 获取文档顶端与屏幕顶部之间的距离
            // scrollTop指的是“元素中的内容”超出“元素上边界”的那部分的高度
            let documentScrollTop = document.documentElement.scrollTop || document.body.scrollTop;
            // 获取鼠标相对于屏幕的坐标
            let mouseClientX = e.clientX
            let mouseClientY = e.clientY
            // 获取小照片相对于屏幕位置信息
            // getBoundingClientRect()用于获得页面中某个元素的左，上，右和下分别相对浏览器视窗的位置。
            let minImgPosition = this.$refs.minImg.getBoundingClientRect();
            let minImgX = minImgPosition.left;
            let minImgY = minImgPosition.top;
            // 计算出探测块相对于小图片的坐标
            let areaLeft = mouseClientX - minImgX - this.areaWidth / 2
            let areaTop = mouseClientY - minImgY - this.areaHeight / 2
            if (documentScrollTop > 0) {
                areaTop = documentScrollTop + areaTop
            }
            let minLeft = 0
            let maxLeft = this.imgBoxWidth - this.areaWidth
            let minTop = 0
            let maxTop = this.imgBoxHeight - this.areaHeight
            // 禁止探测块移出小图片
            if (areaLeft < minLeft) {
                areaLeft = minLeft
            }
            if (areaLeft > maxLeft) {
                areaLeft = maxLeft
            }
            if (areaTop < minTop) {
                areaTop = minTop
            }
            if (areaTop > maxTop) {
                areaTop = maxTop
            }
            // 更新探测块的坐标
            this.$set(this.areaMarkStyle, 'left', areaLeft + 'px')
            this.$set(this.areaMarkStyle, 'top', areaTop + 'px')
            // 更新放大后照片的坐标
            this.$set(this.maxImgStyle, 'left', (this.scale - 1) * this.imgBoxWidth / 2 - areaLeft * this.scale + 'px')
            this.$set(this.maxImgStyle, 'top', (this.scale - 1) * this.imgBoxHeight / 2 - areaTop * this.scale + 'px')
        }
    }
}
</script>
<style scoped>
.box {
    border: 1px solid darkgray;
    position: relative;
    overflow: hidden;
    box-sizing: border-box;
}

.areaMark {
    position: absolute;
    background: url(//img-tmdetail.alicdn.com/tps/i4/T12pdtXaldXXXXXXXX-2-2.png);
}

.maxImgBox {
    position: absolute;
    z-index: 999
}
</style>
  
